1. Field of the Invention
The present invention relates to a device for removing a noise, and more particularly, to a device for removing a noise, in which a delay circuit is used for positively removing a noise contained in a signal regardless of a turn of the signal either from high to low or vice versa.
2. Discussion of the Related Art
A conventional device for removing a noise will be explained referring to the attached drawings. FIG. 1 illustrates a conventional device for removing a noise, and FIG. 2 illustrates a timing chart of FIG. 1.
Referring to FIG. 1, the conventional device for removing a noise is provided with a delay part 1 for delaying a noise occurred in an input signal IN for a fixed time period, and an NAND gate NAND for subjecting the input signal IN and a signal N1 from the delay part to logical production and inversion. The delay part 1 is provided with first, second, third and fourth inverters 11, 12, 13 and 14 each for delaying the noise in the input signal IN for a fixed time period.
The operation of the conventional device for removing a noise will be explained.
Referring to FIG. 2, the conventional device for removing a noise delays the input signal IN through the first, second, third and fourth inverters 11, 12, 13 and 14. In this instance, a noise in a certain interval of the input signal will be also delayed, if any. The NAND gate NAND subjects a signal N1 from the delay part 1 and the input signal to logical production and inversion. Therefore, even if a noise was contained in an input signal, the input signal having the noise removed therefrom is provided because the input signal is delayed for a fixed time period and the delayed signal and the input signal are subjected to logical production and inversion.
However, the conventional device for removing a noise has the following problems.
Though the noise in the input signal contained at a high state can be removed, the noise in the input signal contained at a low state cannot be removed, completely.
And, a delay part simply with inverters can remove a noise longer than a pure transistor delay with difficulty, as a delay time period of the delay part longer than an interval of the noise can remove the noise, a delay time period of the delay part shorter than the interval of the noise can not remove the noise.